Recovery of chrysene



Patented Apr. 15 1947 RECOVERY OF CHRYSENE Gerard W. Curtis, Edgewater, N. J., assignor to Allied Chemical & Dye Corporation, New York, N. Y., a corporation of New York No Drawing. Application May 12, 1945, Serial No. 593,529

Claims.

This invention relates to separation of chrysene om mate ials containing this substance, particularly from chrysene containing coal tar fractions.

It has been proposed to separate chrysene from a high-boiling coal tar fraction by subjecting this material to several successive extractions with carbon bisulfide, recovering a solid from the carbon bisulfide solution, recrystallizing this solid from pseudocumene, subliming the recrystallized material, and heating the sublimed product with hydriodic acid and red phosphorus. It has also been proposed to isolate polynuclear hydrocarbons such as chrysene from high-boiling coal tar fractions by first hydrogenating the fractions, subjecting the hydrogenated product to fractional distillation, dehydrogenating the fraction containing the hydrogenated chrysene, crystallizing a chrysene-containing mixture from this product, extracting the chrysene with carbon bisulfide, and recrystallizing.

These methods have been found unsatisfactory with respect to yield, purity of product, and cost. In fact, it was found that no chrysene could be obtained by these prior art methods from some coal tar fractions which have served as a satisfactory source of chrysene when worked up in accordance with the process of the present invention.

It is an object of this invention to provide a simplified process for recovering chrysene from materials containing this substance in better yield and higher purity of product than has been possible with prior art methods.

It is a further object of this invention to provide a process by means of which chrysene may be recovered from a number of coal tar fractions from which it has not been possible to separate the chrysene by prior art methods.

I have discovered that a product of high chrysene content, c. g. containing about 60% chrysene, may be separated from materials containing chrysene in amounts as low as 5% by subjecting the material to the solvent action of a normally liquid substance containing the pyridine nucleus and boiling below about 237 C; and recovering a solid product high in chrysene. My invention may be carried out by agitating the tar base and chrysene fraction at elevated temperatures and then cooling to recover a solid product rich in chrysene or the treatment may be carried .out at ordinary temperatures, whereupon the tar base will exert a selective solvent action on nonchrysene components, leaving as solid residue a product high in chrysene.

The high-chrysene product thus produced, as above stated, generally contains about chrysene. A substantial proportion of the non-chrysene components of this product may be removed by washing the material with or recrystallizing it from a solvent in which chrysene is readily soluble at elevated temperatures and only slightly soluble at ordinary temperatures, e. g. :a solvent such as ether, alcohols, aromatic hydrocarbons such as benzene, toluene, and xylene, tetralin, decalin and analogous materials. The chrysene product may contain certain highly-colored impurities which, although present in very small amount, tend to give the product a yellow color. These highly-colored impurities may advantageously be removed by heating the chrysene material in solution with maleic anhydride. A white chrysene product of high purity is thus obtained. It is generally advantageous to subject this product to further thorough washing with an organic solvent as above described. followed by slurrying first with dilute aqueous alkali solution and then with dilute aqueous acid solution, to produce a white chrysene product of 99% to 100% purity melting in the range .255258 C. Upon recrystallization, e. g. from pyridine or other suitable solvent of chrysene, chrysene of substantially 3.00% purity crystallizes out in the form of flat white crystals having a pale blue fiuoresence.

The coal tar fractions in which chrysene generally occurs are the high-boiling coal tar oils, containing substantial amounts of neutral constituents boiling above 375 C. For example, a satisfactory source of chrysene was found to be a fraction prepared by distillation of a heavy coal tar oil distillate with superheated steam, having a boiling range corresponding to a range of about 385 to 470 C. at atmospheric pressure; the initial boiling point of this fraction was 385 C. and 45% distilled below 400 C. when tested by A. S. T. .M. Method D 20-30. It was estimated to contain about 5% chrysene. A yield of about 2.5% chrysene based on the oil is obtained from this fraction by the process of the invention. Another example of a coal tar distillate satisfactory as a source of chrysene is the fraction having an initial boiling point of 390 C., 9% of which distills below 400 0. when tested by A. S. T. M. Method D 20-30, the material having a boiling range, recalculated to atmospheric pressure, of 390-500 C. The chrysenecontaining coal tar fractions suitable for treatment are generally obtained as the highest boiling fractions by distilling coal tar or derivative products, particularly creosote oils. The distillations are generally carried out under reduced pressures or by the aid of superheated steam and the products have a boiling range of 385 to 500 C., recalculated to atmospheric pressure. Such fractions constitute pasty mixtures of crystals and oils, which generally become limpid at 70-80 C. Products of petroleum origin in which chrysene is present may also be treated by the process of this invention.

In carrying out the process of my invention the chrysene-containing fraction is subjected to the solvent action of a normally liquid (i. e.. liquid at C.) substance containing the pyridine nucleus and boiling below about 237 C., a solid rich in chrysene being recovered. The substance employed to treat the chrysene fraction thus may be pyridine, the picolines or lutidines or any other normally liquid tar base boiling below about 237 C., or mixtures thereof. The pyridine base may be utilized in substantially pure form or wide or narrow boiling coal tar fractions containing substantial amounts of such pyridine bases may be used; thus the tar base fraction boiling from 150 to 200 C. recovered in the fractionation of coal tar and containing 2,4-lutidine, 2,4,6-collidine and other lutidines and collidines may advantageously be employed. The amount of solvent employed should be such that upon heating and agitating the mixture substantially all the organic components of the chrysene fraction dissolve to form a homogeneous solution.

In a preferred method of practicing my inven-' tion, a chrysene-containing fraction similar to those above described is melted and mixed with about half its weight of pyyridine, and the mixture then stirred until substantially homogeneous, cooled and filtered. Th filter cake is preferably slurried with toluene, the slurry is filtered, and the solid is dried. When the product thus obtained is yellow in color, it generally contains impurities that may be removed by treatment with maleic anhydride. For this treatment the impure chrysene is advantageously mixed with about one-half its weight of maleic anhydride, the mixture is dissolved in a solvent such as toluene 0r tetralin, and this solution is refluxed for several hours; the solution is then preferably filtered to remove dark, carbonaceous impurities which separate during refluxing. When the product crystallized from the resulting solution still retains a yellow or light-brown color, it is generally advantageous to reflux with maleic anhydride several hours more in the presence of nitrobenzene. A white chrysene product may then be crystallized from the resulting solution. This product is preferably washed with or recrystallized from a solvent such as toluene, tetralin, methanol, pyridine or other tar base, and is then advantageously slurried with a dilute aqueous sodium hydroxide solution, filtered, washed with dilute acetic acid and dried. A substantially 100% pure chrysene in the form of flat white crystals having a pale blue fluorescence is thus obtained.

The followin examples are illustrative of the process of my invention:

Example 1.--A coal tar fraction produced by distillation of a coal tar heavy oil having a specific gravity of above 1.15, was distilled with the aid of superheated steam and a fraction was selected which had an initial boiling point of 385 C. and 45% of which distilled below 400 C. when tested by the A. S. T. M. Method D 20-30. Its total boiling range corresponded to about 385 to 470 C. at atmospheric pressure.

1000 parts by weight of this fraction were melted and about 500 parts by weight of pyridine were added. The mixture was maintained at a temperature of about C. and agitated to obtain complete solution. The solution was then cooled to 5 C., and the yellow solids which separated out were filtered off and washed on the filter with about 200 parts by weight of pyridine. The filter cake was then slurried with about 260 parts by weight of toluene, the slurry was filtered and the solid dried. 30 parts by weight of crude chrysene melting at 2325 to 246.0 C. were thus isolated. This crude chrysene was dissolved in about 430 parts by weight of toluene along with 15 parts by weight of maleic anhydride and refluxed for 3 hours. The product that crystallized out upon cooling of the solution still retained a yellow color. Accordingly, about 25 parts by weight of nitrobenzene were added to the toluene solution of crude chrysene and maleic anhydride and the mixture was further refluxed for about 4 hours. Upon cooling, white crystals of chrysene separated out. This product was filtered and washed with toluene. It was then slurried with a small amount of 5% aqueous sodium hydroxide solution, filtered, washed 0n the filter with dilute acetic acid and dried. 22 parts by weight of chrysene melting at 255.6 to 258.6 C., a white solid with a pale blue fluorescence, were thus obtained.

Example 2.A coal tar fraction was produced by distillation with superheated steam of the same coal tar heavy oil as described in Example 1, except that the next higher boiling fraction was selected in this case; this fraction had an initial boiling point of 390 C. and 9% thereof distilled below 400 C. Its boiling range was about 390 to 500 C. at atmospheric pressure.

1000 parts by weight of this fraction and about 750 parts of pyridine were heated on a steam bath until all of the material in the fraction dissolved. The solution was cooled to 5 C. to recrystallize out a solid phase. The solid product was filtered ofi, washed with parts by weight of pyridine, and then about 215 parts by weight of toluene. At this point the filter cake was dark brown and still retained a strong odor of pyridine. It was then slurried with another 215 parts by weight of toluene at room temperature, filtered and dried. 26 parts by wei ht of a yellowishbrown powder, melting at 235 to 240 C., were thus obtained. This product, together with 10 parts by Weight of maleic anhydride, was dissolved in about 300 parts by weight of hot tetralin and heated under reflux for 2 /2 hours. During this time a considerable amount of carbonaceous material separated out. The solution was then poured off from the precipitated material, cooled, and the crystallized chrysene product was filtered off. This product was washed with about 50 parts of tetralin and then with about 87 parts of toluene. It was then slurried with a sma l amount of aqueous sodium hydroxide solution, filtered, and washedwith dilute acetic acid. A yield of 21 parts by weight of chrysene, melting point 253.8 to 257.1 C., was obtained.

Since certain changes may be made in carrying out the above process without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense. a

I claim:

1. Iii a process for isolation of chrysene from a chrysene-containing material, the improvements which comprise subjecting the material to the solvent action of a normally liquid substance containing the pyridine nucleus and boiling below about 237 0., and recovering a solid phase containing chrysene.

2. In a process for isolation of chrysene from a chrysene-containing coal tar fraction, the improvements which comprise subjecting the coal tar fraction to the solvent action of a normally liquid substance containing the pyridine nucleus and boiling below about 237 C., and recovering a solid phase containing chrysene.

3. In a process for isolation of chrysene from a ohrysene-containing coal tar fraction, the improvements which comprise mixing the coal tar fraction with pyridine, heating and agitating the mixture, cooling the resulting solution to precipitate out a solid phase containing chrysene and recovering this solid.

4. In a process for isolation of chrysene from a chrysene-containing coal tar fraction, the improvements which comprise mixing the coal tar fraction with pyridine and recovering from said mixture a solid phase comprising predominantly chrysene.

5. A process for isolation of chrysene from a chrysene-containing coal tar fraction comprising mixing the coal tar fraction with an amount of pyridine sufiicient substantially to dissolve the fraction at elevated temperatures, heating and agitating the mixture to form a substantially homogeneous solution, cooling the solution to precipitate out a solid phase comprising predominantly chrysene, separating this solid and washing it to remove adhering mother liquor, redissolving said solid and treating the solution thus obtained at an elevated temperature with maleic anhydride, recrystallizing the solid from said solution, and Washing the solid to remove adhering mother liquor, thereby producing a highly pure chrysene product.

GERARD W. CURTIS.

REFERENCES CITED 20 The following references are of record in the Name Date Jager et a1 Sept. 27, 1932 Number 

